1. Field of the Invention
This invention relates generally to pilot pressure operated poppet valves and more specifically concerns a three-way, high pressure, pilot pressure operated poppet valve having a guided and stabilized pressure responsive valve piston which supports spaced polymer/elastomer seal assemblies that are designed for high pilot pressure operation in the range of 5,000 psi or greater and high working pressure in the range of 10,000 psi or greater and with seal structure and valve components interrelated to ensure minimum pressure induced extrusion of the seal material and long service life at these high pressure ranges.
2. Description of the Prior Art
While pilot operated poppet valves have been employed for many years, problems have been encountered with poppet valves that operate under high pressure conditions. Particularly, seal damage or detriation occurs by pressure induced extrusion of seal material into gaps between mechanical surfaces. When so extruded, the sealing material can be subject to a condition known as "nibbling" wherein the sealing material is pinched between metal surfaces to the extent that minute sections of the sealing material are cut and broken away. When this condition occurs, especially when it occurs repetitiously, the sealing capablity of the seal can become degraded to the point that valve leakage occurs. It is necessary in this case, to either replace the valve or to replace the damaged sealing elements of the valve to thus restore it to operational condition. The problem of seal nibbling is accenuated under circumstances where the gland of the valve or the valve seat are subject to potential lateral movement such as due to pressure induced vibration or misalignment of valve components during opening and closing movement. For example, if sealing material is pressure extruded into a gap between mechanical valve components and one of the valve components is move laterally, such as by vibration or other pressure induced force, the extruded section of the sealing material can be severly pinched, so that it is either cut away or deformed beyond its elastic limits so that it becomes degraded. Further, high velocity flow of high pressure fluid through a gap of minimal dimension between a valve seat and valve seal can subject the exposed sealing material to high pressure erosion which also degrades the sealing material to the point that its sealing capability can be lost. It is desirable, therefore, to provide a poppet valve mechanism having one or more high pressure seal assemblies, each of which is protected against pressure induced extrusion, nibbling or pressure induced deteriation.
Efforts have been made in the past to design poppet type valves that are responsive to relatively high pressure conditions. U.S. Pat. No. 3,131,722 of Abbott, et al shows a three-way valve that is designed for quick shifting characteristics. The various the seal elements of this valve are in the form of simple O-rings that are located in unsupported relation within seal grooves. A spacer element 22 is employed between the spaced seal glands. The unsupported elastomer seals of Abbott, et al will deteriorate quite readily under the high pressure conditions for which the valve of the present invention is designed. For example, U.S. Pat. No. 3,736,960 of Cohen discloses a snap-acting, fluid amplifing valve including a piston and piston stem arrangement. The spring urged piston has a lower piston element 45 having flat upper and lower elastomer seals for sealing engagement with tapered vent and supply nozzles. These elastomer seals will become damaged quite readily by the influence of high pressure fluid service.
U.S. Pat. No. 3,805,837 of Stampfli discloses a control valve arrangement having a piston that incorporates flap valves 3 and 4 which are spaced by a core 2 in the form of a spool-like member. Only the radially inner portions of the seals of the opposed glands are supported by the spool member 2. Thus, the relatively unsupported elastomer sealing elements will function properly only under average operational pressure conditions. When high working pressures in the range of 10,000 psi are encountered, these unsupported seals will fail quite readily; in fact, they will be readily extruded from their grooves and will be subject to nibbling and other damage. U.S. Pat. No. 3,977,438 of Muchow, et al discloses a pilot valve arrangement having a reset mechanism and having a spool member 35 with a valve head 36 at its lower end and having upper and lower seals that are captured in circular recesses by respective retainer rings or washers. These resilient seals, which may be O-ring type seals, are positioned for engagment with sharp circular seat corners such as shown at 38. These seals, under even nominally high pressure conditions, will be subject to pressure induced erosion, nibbling or other deterioration. The present invention is designed to overcome the disadvantages of the valve seal arrangements that are disclosed in the above identified U.S. Patents and to provide for efficient sealing under extremely high pressure conditions while protecting against pressure induced extrusion, seal nibbling, fluid erosion and other factors that might otherwise result in seal deterioration and resulting valve failure.